1.VerbTo do something insufficiently; especially, to undercook.
"Sorry to say, I've underdone the pot roast. I think we'd better put it back in the oven for a bit.; Sorry to say, I've underdone the downspout repair. I think we'd better hire someone to replace the whole thing.; We warned him not to underdo it. This customer expects attention to detail."
2.VerbTo do less than is requisite.
"We warned him not to underdo it. This customer expects attention to detail."
3.VerbTo act below one's abilities; do less than one can.